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Now i am worried!

I read in a recent thread about the HDS lights that: 'Potted electronics which usually means that it would be one of the rare lights that would work in case of an EMP pulse hit' that was the exact quote, and my question is that, is this true, would my fenix range or most others not work? Because i dont want to be stuck with none of my torches working if that does happen!
Thanks

Re: Now i am worried!

Short version: nobody has done extensive testing of modern-flashlight-type electronics in a nuclear-type EMP, but your lights are the least of your worries in an EMP. The physics of it indicate tightly wrapping your flashlights in the emergency kit in tinfoil, or not worrying much.

Re: Now i am worried!

Several years ago with the introducton of NIMS (National Incident Management Syetem), I took classes from the Feds (FEMA) and State Emergency Management, This subject was brought up, I don't remember if it was part of the course or just a question asked.
I was advised by people who shoud know: "Don't sell off your old electronic equipment or scrap it. Store some of it in sealed ammo cans, and put some of it back, The event of an EMP strike is not great, however the Sun is capible of doing just as much dammage at any time." At least at the time (5 years ago) I was told " Ammo cans will sheild electronic devices quite well as long as a cardboard or similar barrier is placed inside to keep the objects from contacting the top, sides or bottom of the can" I was also advised that a Gun Save with a carpeted interior should serve the same prupose. Hope this helps.

Re: Now i am worried!

Originally Posted by whiteoakjoe

Several years ago with the introducton of NIMS (National Incident Management Syetem), I took classes from the Feds (FEMA) and State Emergency Management, This subject was brought up, I don't remember if it was part of the course or just a question asked.
I was advised by people who shoud know: "Don't sell off your old electronic equipment or scrap it. Store some of it in sealed ammo cans, and put some of it back, The event of an EMP strike is not great, however the Sun is capible of doing just as much dammage at any time." At least at the time (5 years ago) I was told " Ammo cans will sheild electronic devices quite well as long as a cardboard or similar barrier is placed inside to keep the objects from contacting the top, sides or bottom of the can" I was also advised that a Gun Save with a carpeted interior should serve the same prupose. Hope this helps.

electricity remains on the outside surface, no need for cardboard or any other insulator inside

Re: Now i am worried!

Originally Posted by Fireclaw18

I assume if you didn't wrap your light in foil then EMP probably would kill it, since the LED is probably outside any shielding provided by the metal flashlight body?

Yeah, a metal flashlight body can actually acts like an antenna for the EMP if it is used in the flashlight's circuit. You need to wrap the foil over a layer of insulation so it doesn't touch the flashlight.

Re: Now i am worried!

To answer the OPs question, no. Potting will absolutely no protect a circuit from an EMP. If the entire flashlight was covered with electrically conductive potting (does defeat the purpose of potting though) It still wouldn't work. The Faraday cage relies on an isolated conductive "shell" to work properly. As someone above said, if you allow something conductive to make contact with the cage... It would actually act as more of an antenna then a protective cage.

Originally Posted by 127.0.0.1

electricity remains on the outside surface, no need for cardboard or any other insulator inside

same with an emp. outside, not inside.

That isn't always true. If you properly ground it, than yes. If it is an ungrounded container (like an ammo can) then you do in fact need to make sure that it is not in direct contact with unpainted metal. You also need to make sure that the lid and the box are electrically tied (bonded)

Re: Now i am worried!

Originally Posted by BobBarker

... The Faraday cage relies on an isolated conductive "shell" to work properly. As someone above said, if you allow something conductive to make contact with the cage... It would actually act as more of an antenna then a protective cage.

The electrical field will always be zero inside a metal shell. No need to insulate.

You also want to ground it to dissipate any electrical charge that may build up but it is not necessary for it to act as a Faraday cage.

Have a tritium vial to install? See my sales thread for Norland 61 optical adhesive.

Re: Now i am worried!

The electrical field will always be zero inside a metal shell. No need to insulate.

You also want to ground it to dissipate any electrical charge that may build up but it is not necessary for it to act as a Faraday cage.

A metal flashlight is not a true faraday cage. The led and switch areas are not covered and is wide open. Also, lots of metal lights use the metal body as part of the circuitry and will conduct the EMP right into the electronics.

Re: Now i am worried!

Originally Posted by Pandorum

A metal flashlight is not a true faraday cage. The led and switch areas are not covered and is wide open. Also, lots of metal lights use the metal body as part of the circuitry and will conduct the EMP right into the electronics.

Right. But I never said a flashlight is a Faraday cage. If you look at what I quoted, I was replying to the comment that the flashlight cannot make contact with the inside of the cage or it will act as antenna, which is not correct.

Have a tritium vial to install? See my sales thread for Norland 61 optical adhesive.

Re: Now i am worried!

Originally Posted by LightWalker

How do you figure this? Are you an expert on the intentions of national leaders? Have you not heard the threats made by some national leaders?

+2

I, by the way, am an expert on the intentions of the hearts of chief of states AS WELL AS rogue leaders and I say there will be a nuclear blast in the next 14 months. I'm thinkin it'll probably happen on a Monday... could be Thursday, but I'm gonna go with Monday!

Re: Now i am worried!

Originally Posted by RocketTomato

Right. But I never said a flashlight is a Faraday cage. If you look at what I quoted, I was replying to the comment that the flashlight cannot make contact with the inside of the cage or it will act as antenna, which is not correct.

But that is correct.
If the flashlight is metal and contacts the inside of the faraday cage then the EMP energy can be transmitted to the flashlight and damage its electronics. You do need to insulate the object you're trying to protect.

Re: Now i am worried!

The electrical field will always be zero inside a metal shell. No need to insulate.

You also want to ground it to dissipate any electrical charge that may build up but it is not necessary for it to act as a Faraday cage.

The cage only works if the item you are protecting is not making direct electrical contact with the cage. The separation (or insulation) required to achieve this effect is dependent on the strength of the spike. Just putting a flashlight (or anything else with closely spaced electrical traces, like ICs) in the cage (assuming direct aluminum to cage contact, or a spike of sufficient voltage to overcome the insulation) will in fact not protect anything.

Think about it like this. A Faraday cage works as well keeping signals (emp) out as well as it does keeping it in. But if you were to take a transmitter and make a direct electrical contact with the cage, it now becomes a very poorly designed antenna.

This was one of many things stressed to us during the EMP hardening classes I had to take on aircraft avionics.

Re: Now i am worried!

Originally Posted by BobBarker

Think about it like this. A Faraday cage works as well keeping signals (emp) out as well as it does keeping it in. But if you were to take a transmitter and make a direct electrical contact with the cage, it now becomes a very poorly designed antenna.

I'm interested in aircraft avionics because they operate high up in the atmosphere, and encounter exciting solar flare effects. Nobody has tested a commercial jetliner near the poles in a solar flare due to safety things (As far as I know!).

With flashlights, this is just one more reason to appreciate anodization. Although if you're going to go all-out in having your EDC ready for use, I suggest this procedure based on me making things up before morning coffee.

1. Place flashlight in a ziploc bag. Seal bag, then roll around light. Flashlight is now waterproof.
2. Wrap in fabric to provide an electrical and impact buffer.
3. Wrap in foil, place in gallon ziplock. If you want to be clever about the foil, run a fishing line in the wrappings so you can pull it and 'unzip' the foil wrapping.
4. Place bag someplace secure. The light will probably survive an earthquake or two, and need battery changes every so often.

Re: Now i am worried!

Yeah, contact that creates continuity with the metal of the "cage" essentially makes the conductive contact materials PART of the cage, defeating the purpose.

Similarly, if the light uses its body as part of a circuit, the body is not protecting the circuit. After all that, it comes down to a matter of DEGREE. The effective strength of the effect in that orientation, etc, and, the durability relative to that sort of energy involved of the circuit in question, will determine if the effect actually causes any damage.

Remember that solar effects are a regular occurrence, and that EMP exposure to your lights has already occurred many times....so if they work NOW, they already have at least some resistance to this effect.

In addition to your flashlight, the things that charge your cells, operate your car and computer, etc, are also vulnerable. Are you going to wrap your rig, chargers, and computer, etc, in foil when not in use so they also survive?

Re: Now i am worried!

I'm pretty certain that the destructive effects of EMP on electronic components is vastly overstated. Mostly, this is due to worried preparedness types that would rather try to advise as experts, rather than truly understand the issue at hand.

EMP resulting from an airburst nuclear detonation is far more localized and limited than it is proclaimed to be. Those that are wrapping everything in layers of tinfoil and burying hand-crank Ford Model T's for their post-apocolyptic fantasy are going to be a bit sore when they realize that their neighbor's iPad and Prius start right up. The most worrisome effects of EMP is immediate effects to distribution infrastructure (that will mostly be blown up anyways), and lingering ionization that will affect all electromagnetic communication for a decreasing period of time. The most worrisome would be sensitive satellite electronics. As correctly pointed out, the sun dishes out similar EM radiation regularly.

In other words, if you are close enough to a blast for your kit to be affected by EMP, it's already a miracle that the heat and blast effects didn't already kill you. The radiation dose you received in that blast will likely kill you before you have a chance unwrap your cell phone from the reynolds wrap though.

This sentiment that a single EMP burst above the continental US as a giant "Off Switch" is pure lunacy, but it gets repeated all over the web. Tinfoil is for wrapping leftovers, not your head and electronics.